The code sent to me on Xbox live for the Halo 4 specializations is coming back as invalid. I would have posted this in the large thread (which I was linked to via the xbox support forums) but that thread is now closed (or locked? Im not sure). Xbox support told me that to follow up on this I would want to post this here.
I am over 17 and I played on the night of the release so definitely before 11/20.
Thanks!